1. Field of the Invention
The present invention relates to optically sensing manufacturing defects in organic photo conductors (OPC) and, more particularly, to detecting bottom edge wipe in the manufacture of OPCs.
2. Prior Art
Cylindrical aluminum organic photo conductor (OPC) substrates undergo dip-coating process by vertically immersing the cylindrical OPC in a dip tank. After dipping it is required that the trailing edge of the part must meet certain specifications in order to avoid bottom edge wipe defects (i.e., where dip coating residue remains on the bottom of the OPC). FIG. 5 shows that bottom edge wipe (BEW) defects are the most common of defects caused by the dipping process. However, existing automatic visual inspection (AVI) systems are not designed to inspect for BEW defects. The existing AVI systems only inspect for defects within the image area of the OPC and ignores the areas outside the image area, i.e., the bottom edge area. Yet, the interface of the bottom edge area within larger systems and subsystems is critical to the performance of such systems. For this reason, the OPC bottom edge area is subjected to an outgoing quality control, but not until after value is added to the defective OPC at several other stages in the manufacturing process prior to the quality control check. Thus, the failure to detect BEW defects early in the manufacturing process results in decreased productivity as well as lost value.